Zsh users: In the instructions above substitute ~/.bash_profile with ~/.zshenv.

Note: You may need to add source ~/.bash_profile to ~/.profile depending upon your bash configuration.

Alternate Installation Using Homebrew

If you use Homebrew on Mac OS X you may prefer to install rbenv like this:

brew update

brew install rbenv

brew install ruby-build

Install Ruby 1.9.3

Next install Ruby 1.9.3 and you'll be all set.

rbenv install 1.9.3-p0

rbenv local 1.9.3-p0

rbenv rehash

Note:rbenv local 1.9.3-p0 ensures that your Octopress installation is using Ruby 1.9.3-p0 without modifying your environment in any other directory. If you wish to use 1.9.3-p0 everywhere, run rbenv global 1.9.3-p0 instead.

Run ruby --version to be sure you're using Ruby 1.9.3. If you're having trouble, seek help here